Method for making carbon nanotube composite structure

ABSTRACT

A method for making a carbon nanotube composite structure is provided. First, a matrix having a surface and a carbon nanotube structure are provided. The carbon nanotube structure is placed on the surface of the matrix. The carbon nanotube structure includes a plurality of carbon nanotubes. The carbon nanotube structure and the matrix are exposed to electromagnetic waves.

RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. §119 fromChina Patent Application No. 201010524918.8, filed on Oct. 29, 2010 inthe China Intellectual Property Office, the disclosure of which isincorporated herein by reference. The application is also related tocopending applications entitled, “METHOD FOR BONDING MEMBERS”, filed______ (Atty. Docket No. US36174); “CARBON NANOTUBE COMPOSITESTRUCTURE”, filed ______ (Atty. Docket No. US36176).

BACKGROUND

1. Technical Field

The present disclosure relates to composites, particularly, to a carbonnanotube composite structure and a method for making the same.

2. Description of Related Art

Carbon nanotubes (CNT) are a novel carbonaceous material havingextremely small size and extremely large specific surface area. Carbonnanotubes have interesting and potentially useful electrical andmechanical properties, and have been widely used in a plurality offields such as emitters, gas storage and separation, chemical sensors,and high strength composites.

However, the main obstacle in applying carbon nanotubes is thedifficulty in processing the common powder form of the carbon nanotubeproducts. Therefore, forming separate and tiny carbon nanotubes intomanipulable carbon nanotube structures is necessary.

Carbon nanotube composite structure is one kind of manipulable carbonnanotube structures. A method for producing many carbon nanotubecomposite structures includes a stirring step or vibration step todisperse carbon nanotube powder in the composite matrix. However, carbonnanotubes have extremely high surface energy and are prone to aggregate.Therefore, it is very difficult to achieve a composite with carbonnanotubes evenly dispersed therein. Furthermore, the carbon nanotubesare dispersed in the whole matrix in the carbon nanotube compositestructure produced by this method, conductivity of a surface of thecarbon nanotube composite structure is low, which limits the applicationof the carbon nanotube composite structure.

What is needed, therefore, is a carbon nanotube composite structure andmethod for making the same that can overcome the above-describedshortcomings.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with referencesto the following drawings. The components in the drawings are notnecessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the embodiments.

Moreover, in the drawings, like reference numerals designatecorresponding parts throughout the several views.

FIG. 1 is a flow chart according to one embodiment of a method formaking a carbon nanotube composite structure.

FIG. 2 is a Scanning Electron Microscope (SEM) image of a side surfaceof the carbon nanotube composite structure.

FIG. 3 is a schematic view of the side surface of the carbon nanotubecomposite structure.

FIG. 4 is a photo of a surface of the carbon nanotube compositestructure and a magnifying photo of part of the surface of the carbonnanotube composite structure.

FIG. 5 is a schematic view of the surface of the carbon nanotubestructure in FIG. 4.

FIG. 6 is an SEM image of a top surface of the carbon nanotube compositestructure.

FIG. 7 is a schematic view of the top surface of the carbon nanotubecomposite structure in FIG. 6.

FIG. 8 is a photo of the wetting quality of the carbon nanotubestructure located on the surface of the matrix without dealing withmicrowaves.

FIG. 9 is a schematic view of FIG. 8.

FIG. 10 is a photo of the wetting quality of the carbon nanotubecomposite structure.

FIG. 11 is a schematic view of FIG. 10.

DETAILED DESCRIPTION

The disclosure is illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” embodiment in this disclosure are not necessarily tothe same embodiment, and such references mean at least one.

One embodiment of a method for making a carbon nanotube compositestructure is illustrated in FIG. 1. The method includes the followingsteps:

(a) providing a matrix having a surface and a carbon nanotube structure;

(b) placing the carbon nanotube structure on the surface of the matrix,the carbon nanotube structure including a plurality of carbon nanotubesand a plurality of pores; and

(c) exposing the carbon nanotube structure and the matrix toelectromagnetic waves.

In step (a), the matrix can be made of ceramic, glass, or polymericmaterials. Examples of the polymeric materials comprise polyethylene,epoxide resin, bismaleimide resin, cyanate resin, polypropylene,polyethylene, polyvinyl alcohol, polystyrene enol, polycarbonate, andpolymethylmethacrylate. The shape of the matrix is not limited. In oneembodiment, the matrix is a cuboid made of polyethylene, a thickness ofthe matrix is about 3 millimeters. The surface is a square, and a sideof the surface is about 50 millimeters.

In step (b), the carbon nanotube structure includes a plurality ofcarbon nanotubes combined by van der Waals force therebetween. Thecarbon nanotube structure can be a substantially pure structure of thecarbon nanotubes, with few impurities. The heat capacity per unit areaof the carbon nanotube structure can be less than 2×10^(—4) J/m²*K. Inone embodiment, the heat capacity per unit area of the carbon nanotubestructure 120 is less than or equal to 1.7×10−6 J/m²*K. As the heatcapacity of the carbon nanotube structure 120 is very low, this makesthe carbon nanotube structure have a high heating efficiency, a highresponse heating speed, and accuracy. Furthermore, the carbon nanotubeshave a low density, about 1.35 g/cm³, so the carbon nanotube structureis light. The carbon nanotube structure includes a plurality ofmicropores, and diameters of these micropores can be less than 10micrometers. As the carbon nanotube has large specific surface area andthe carbon nanotube structure includes a plurality of micropores, thecarbon nanotube structure with a plurality of carbon nanotubes has largespecific surface area. When the specific surface of the carbon nanotubestructure is large enough, the carbon nanotube structure is adhesive andcan be directly applied to a surface. The carbon nanotube structure canbe adhered on the surface directly without extra adhesive material.

The carbon nanotubes in the carbon nanotube structure can be orderly ordisorderly arranged. The term ‘disordered carbon nanotube structure’refers to a structure where the carbon nanotubes are arranged alongdifferent directions, and the alignment directions of the carbonnanotubes are random. The number of the carbon nanotubes arranged alongeach different direction can be almost the same (e.g. uniformlydisordered). The disordered carbon nanotube structure can be isotropic,namely the carbon nanotube film has properties identical in alldirections of the carbon nanotube film. The carbon nanotubes in thedisordered carbon nanotube structure can be entangled with each other.

The carbon nanotube structure can be an ordered carbon nanotubestructure. The term ‘ordered carbon nanotube structure’ refers to astructure where the carbon nanotubes are arranged in a consistentlysystematic manner, e.g., the carbon nanotubes are arranged approximatelyalong a same direction and/or have two or more sections within each ofwhich the carbon nanotubes are arranged approximately along a samedirection (different sections can have different directions). The carbonnanotubes in the carbon nanotube structure 120 can be selected fromsingle-walled, double-walled, and/or multi-walled carbon nanotubes. Thecarbon nanotube structure includes at least one carbon nanotube film.The carbon nanotube film can be a drawn carbon nanotube film, a pressedcarbon nanotube film, or a flocculated carbon nanotube film.

The drawn carbon nanotube film includes a plurality of successive andoriented carbon nanotubes joined end-to-end by van der Waals forcetherebetween. The drawn carbon nanotube film is a free-standing film. Amethod of making a drawn carbon nanotube film includes the steps of:

-   Sb1: providing an array of carbon nanotubes; and-   Sb2: pulling out at least a drawn carbon nanotube film from the    carbon nanotube array.

In step Sb1, a method of making the array of carbon nanotubes includes:

-   Sb11: providing a substantially flat and smooth substrate;-   Sb12: applying a catalyst layer on the substrate;-   Sb13: annealing the substrate with the catalyst at a temperature in    the approximate range of about 700° C. to about 900° C. in air for    about 30 to about 90 minutes;-   Sb14: heating the substrate with the catalyst at a temperature in    the approximate range from about 500° C. to about 740° C. in a    furnace with a protective gas therein; and-   Sb15: supplying a carbon source gas to the furnace for about 5 to    about 30 minutes and growing a super-aligned array of the carbon    nanotubes from the substrate.

In step Sb11, the substrate can be a P or N-type silicon wafer. In oneembodiment, a 4-inch P-type silicon wafer is used as the substrate.

In step Sb12, the catalyst can be made of iron (Fe), cobalt (Co), nickel(Ni), or any combination alloy thereof.

In step Sb14, the protective gas can be made up of at least one ofnitrogen (N₂), ammonia (NH₃), and a noble gas.

In step Sb15, the carbon source gas can be a hydrocarbon gas, such asethylene (C₂H₄), methane (CH₄), acetylene (C₂H₂), ethane (C₂H₆), or anycombination thereof.

In step Sb2, the drawn carbon nanotube film can be fabricated by thesteps of:

-   Sb21: selecting one or more carbon nanotubes having a predetermined    width from the array of carbon nanotubes; and-   Sb22: pulling the carbon nanotubes to obtain nanotube segments at an    even/uniform speed to achieve a uniform carbon nanotube film.

In step Sb21, the carbon nanotube segment includes a number ofsubstantially parallel carbon nanotubes. The carbon nanotube segmentscan be selected by using an adhesive tape as the tool to contact thesuper-aligned array of carbon nanotubes. In step Sb22, the pullingdirection can be substantially perpendicular to the growing direction ofthe super-aligned array of carbon nanotubes.

More specifically, during the pulling process, as the initial carbonnanotube segments are drawn out, other carbon nanotube segments are alsodrawn out end to end due to van der Waals force between ends of adjacentsegments. This process of pulling produces a substantially continuousand uniform carbon nanotube film having a predetermined width can beobtained.

After the step of Sb2, the drawn carbon nanotube film can be treated byapplying organic solvent to the drawn carbon nanotube film to soak theentire surface of the carbon nanotube film. The organic solvent isvolatile and can be selected from ethanol, methanol, acetone,dichloromethane, chloroform, or any appropriate mixture thereof. In theone embodiment, the organic solvent is ethanol. After being soaked bythe organic solvent, adjacent carbon nanotubes in the carbon nanotubefilms that are able to do so, bundle together, due to the surfacetension of the organic solvent when the organic solvent is volatilizing.In another aspect, due to the decrease of the specific surface area fromthe bundling, the mechanical strength and toughness of the drawn carbonnanotube film are increased and the coefficient of friction of thecarbon nanotube films is reduced. Macroscopically, the drawn carbonnanotube film will be an approximately uniform film.

The width of the drawn carbon nanotube film depends on the size of thecarbon nanotube array. The length of the drawn carbon nanotube film canbe set as desired. In one embodiment, when the substrate is a 4 inchtype wafer, a width of the carbon nanotube film can be in an approximaterange from 1 centimeter (cm) to 10 cm, the length of the carbon nanotubefilm can reach to about 120 m, the thickness of the drawn carbonnanotube film can be in an approximate range from 0.5 nm to 100 microns.Multiple films can be adhered together to obtain a film of any desiredsize.

If the carbon nanotube structure includes a number of stacked drawncarbon nanotube films, and the number of the stacked drawn carbonnanotube films are fabricated according to following steps:

-   (1) providing a number of drawn carbon nanotube film, adhering one    drawn carbon nanotube film to a frame;-   (2) depositing other drawn carbon nanotube films on the preceding    drawn carbon nanotube film successively, thereby achieving at least    a two-layer drawn carbon nanotube film; and-   (3) peeling the plurality of stacked drawn carbon nanotube films off    the frame to achieve the plurality of stacked drawn carbon nanotube    films.

The carbon nanotubes in the pressed carbon nanotube film are arrangedalong a same direction or along different directions. The carbonnanotubes in the pressed carbon nanotube film can rest upon each other.A method of making the pressed carbon nanotube film includes thefollowing steps:

Sb1′: providing a carbon nanotube array and a pressing device; and

Sb2′: pressing the array of carbon nanotubes to obtain a pressed carbonnanotube film.

In step Sb1′, the carbon nanotube array can be made by the same methodas Sb1.

In the step Sb2′, a certain pressure can be applied to the array ofcarbon nanotubes by the pressing device. In the process of pressing, thecarbon nanotubes in the array of carbon nanotubes separate from thesubstrate and obtain the carbon nanotube film under pressure. The carbonnanotubes are substantially parallel to a surface of the carbon nanotubefilm.

In one embodiment, the pressing device can be a pressure head. Thepressure head has a smooth surface. The shape of the pressure head andthe pressing direction can determine the direction of the carbonnanotubes arranged therein. When a pressure head (e.g. a roller) is usedto travel across and press the array of carbon nanotubes along apredetermined single direction, a carbon nanotube film having a numberof carbon nanotubes primarily aligned along a same direction isobtained. It can be understood that there may be some variation in thefilm. Different alignments can be achieved by applying the roller indifferent directions over an array. Variations on the film can alsooccur when the pressure head is used to travel across and press thearray of carbon nanotubes several times, variation will occur in theorientation of the nanotubes. Variations in pressure can also achievedifferent angles between the carbon nanotubes and the surface of thesemiconducting layer on the same film. When a planar pressure head isused to press the array of carbon nanotubes along the directionperpendicular to the substrate, a carbon nanotube film having a numberof carbon nanotubes isotropically arranged can be obtained. When aroller-shaped pressure head is used to press the array of carbonnanotubes along a certain direction, a carbon nanotube film having anumber of carbon nanotubes aligned along the certain direction isobtained. When a roller-shaped pressure head is used to press the arrayof carbon nanotubes along different directions, a carbon nanotube filmhaving a number of sections having carbon nanotubes aligned alongdifferent directions is obtained.

The flocculated carbon nanotube film can include a plurality of long,curved, disordered carbon nanotubes entangled with each other.Furthermore, the flocculated carbon nanotube film can be isotropic. Theflocculated carbon nanotube film can be made by the following method:

-   Sb1″: providing a carbon nanotube array;-   Sb2″: separating the array of carbon nanotubes from the substrate to    get a number of carbon nanotubes;-   Sb3″: adding the number of carbon nanotubes to a solvent to get a    carbon nanotube floccule structure in the solvent; and-   Sb4″: separating the carbon nanotube floccule structure from the    solvent, and shaping the separated carbon nanotube floccule    structure into a carbon nanotube film to achieve a flocculated    carbon nanotube film.

In step Sb1″, the carbon nanotube array can be fabricated by the samemethod as step Sb1.

In step Sb2″, the array of carbon nanotubes is scraped off the substrateto obtain a number of carbon nanotubes. The length of the carbonnanotubes can be above 10 microns.

In step Sb3″, the solvent can be selected from water or volatile organicsolvent. After adding the number of carbon nanotubes to the solvent, aprocess of flocculating the carbon nanotubes can, be suitably executedto create the carbon nanotube floccule structure. The process offlocculating the carbon nanotubes can be selected from ultrasonicdispersion of the carbon nanotubes or agitating the carbon nanotubes. Inone embodiment ultrasonic dispersion is used to flocculate the solventcontaining the carbon nanotubes for about 10˜30 minutes. Due to thecarbon nanotubes in the solvent having a large specific surface area andthe tangled carbon nanotubes having a large van der Waals force, theflocculated and tangled carbon nanotubes obtain a network structure(e.g., floccule structure).

In step Sb4″, the process of separating the floccule structure from thesolvent includes the sub-steps of:

Sb4″1: filtering out the solvent to obtain the carbon nanotube flocculestructure; and

Sb4″2: drying the carbon nanotube floccule structure to obtain theseparated carbon nanotube floccule structure.

In step Sb4″1, the carbon nanotube floccule structure can be disposed inroom temperature for a period of time to dry the organic solventtherein. The time of drying can be selected according to practicalneeds. The carbon nanotubes in the carbon nanotube floccule structureare tangled together.

In step Sb4″2, the process of shaping includes the sub-steps of:

-   -   Sb4″21: putting the separated carbon nanotube floccule structure        on a supporter (not shown), and spreading the carbon nanotube        floccule structure to obtain a predetermined structure;    -   Sb4″22: pressing the spread carbon nanotube floccule structure        with a determined pressure to yield a desirable shape; and    -   Sb4″23: removing the residual solvent contained in the spread        floccule structure to obtain the flocculated carbon nanotube        film.

Through flocculating, the carbon nanotubes are tangled together by vander Waals force to obtain a network structure/floccule structure. Thus,the flocculated carbon nanotube film has good tensile strength.

In one embodiment, the carbon nanotube structure is a drawn carbonnanotube film. The carbon nanotube structure is disposed on the surfaceof the matrix.

In the step (c), a power of the electromagnetic waves can be in a rangefrom about 200 W to about 2000 W. The power of the electromagnetic waveis determined by the melting point of the materials of the matrix. Thehigher the melting points of the materials, the higher the power of theelectromagnetic wave. The electromagnetic wave can be radio frequency,microwave, near infrared or far infrared. In one embodiment, theelectromagnetic waves are microwaves. A power of the microwaves can bein a range from about 200 W to about 1500 W. A frequency of themicrowaves can be in a range from about 1 GHz to about 10 GHz. Thecarbon nanotube structure and the matrix are kept and heated in thechamber filled with microwaves for about 1 second to about 300 seconds.In other embodiments, the carbon nanotube structure and the matrix arekept and heated in the chamber filled with microwaves about 3 seconds toabout 90 seconds. The time the carbon nanotube structure and the matrixheated in the chamber filled with microwaves depends on the material ofthe matrix, and the power of the microwaves. The higher the meltingpoints of the materials of the matrix, the longer the time. The higherthe power of the microwaves, the shorter the time the chamber needs tobe filled. In one embodiment, the time is about 30 seconds.

In the step (c), the carbon nanotube structure is exposed in theelectromagnetic waves until a portion of the matrix is melted andpermeates into pores of the carbon nanotube structure. In oneembodiment, the carbon nanotube structure located on the matrix surfacecan be placed into a chamber filled with electromagnetic waves. Thematerials of the matrix are polymer and barely absorbing energy ofelectromagnetic waves; as such, the matrix will not be heated by theelectromagnetic waves. The carbon nanotube structure located on thesurface of the matrix can absorb the energy of the microwaves andgenerate heat. Because the carbon nanotube structure has a small heatcapacity per unit area, a temperature of the carbon nanotube structurerises quickly. This temperature increase will heat the surface of thematrix until the carbon nanotube structure is able to infiltrate thematrix. In one embodiment, the surface of the matrix is melted by theheat, and liquid matrix is present on the surface. Because wettabilityof the liquid matrix and the carbon nanotube structure is good, theliquid matrix will infiltrate into micropores of the carbon nanotubestructure, as such, the carbon nanotube structure will be coated by theliquid matrix. After the liquid matrix wets the whole carbon nanotubestructure, the material of matrix will stop moving into the microporesand the micropores will be full of the matrix material. In other words,the carbon nanotube structure settle into the matrix, below the surfaceof the matrix. A perpendicular distance D between the surface of thematrix and the carbon nanotubes in the carbon nanotube structure is lessthan 10 micrometers, that is to say, a thickness of part of the matrixabove the carbon nanotube structure is less than 10 micrometers. Theheat generated by the carbon nanotube structure can be absorbed by thesurface of the matrix, and the temperature of the carbon nanotubestructure can be controlled under 700° C., and the carbon nanotubestructure will not burn.

In one embodiment, the matrix is made of polyethylene, which has amelting point of about 137° C., the carbon nanotube structure and thematrix can be kept in the chamber filled with microwaves until thetemperatures of the surface reaches or gets a little higher than themelting point of about 137° C. The carbon nanotube structure and thematrix can be kept in the chamber for about 10 seconds, and the carbonnanotube structure will embed in matrix.

Step (c) can be carried out in vacuum environment of about 10⁻² Pascalsto about 10⁻⁶ Pascals, or in a specific atmosphere of protective gasesincluding nitrogen gas and inert gases. The carbon nanotube structure120 can generate a lot of heat and reach the temperature of about 2000°C. to embed into a matrix, which has high melting points when the carbonnanotube structure 120 works in vacuum environment or in a specificatmosphere.

The method for making the carbon nanotube composite structure has thefollowing advantages: first, the surface of the matrix is heated to formthe carbon nanotube composite structure, there is no need to heat thewhole matrix, the matrix will not be destroyed and energy is saved.Second, the method for making the carbon nanotube composite structurecan keep the thickness of the matrix above the carbon nanotube structureless than 10 micrometers, as such, the surface of the carbon nanotubecomposite structure is conductive. Furthermore, methods, describedherein, for making the carbon nanotube composite are relatively simpleand easy to perform.

Referring to FIGS. 2 and 3, a carbon nanotube composite structure 10made by the above method is also provided. The carbon nanotube compositestructure 10 includes a matrix 12 and a carbon nanotube structure 14.The matrix 12 includes a top surface 122, the carbon nanotube structure14 is embedded in the matrix 12 and below the surface 122. The carbonnanotube structure 14 includes a first surface 142 and a second surface144 opposite with the first surface 142. The first surface 142 is nearthe top surface 122 of the matrix. A perpendicular distance D betweenthe top surface 122 and the first surface 142 of carbon nanotubestructure 14 is less than 10 micrometers. In some embodiments, theperpendicular distance D between the surface 122 and the carbon nanotubestructure is ranged from about 10 nanometers to about 200 nanometers.

The matrix 12 can be ceramic, glass, or polymeric materials. Examples ofthe polymeric materials comprise polyethylene, epoxide resin,bismaleimide resin, cyanate resin, polypropylene, polyethylene,polyvinyl alcohol, polystyrene enol, polycarbonate, andpolymethylmethacrylate. A melting point of the matrix 12 can be lessthan 600° C.

The carbon nanotube structure 14 includes a plurality of carbonnanotubes combined by van der Waals force therebetween. The carbonnanotube structure 14 can be a substantially pure structure of thecarbon nanotubes, with few impurities. A thickness of the carbonnanotube structure can be in a range from about 50 nanometers to about10 micrometers. The carbon nanotube structure 14 includes a plurality ofmicropores, and diameters of these micropores can be less than 10micrometers. The micropores can be defined by distance between adjacentcarbon nanotubes. The carbon nanotubes in the carbon nanotube structure14 can be orderly or disorderly arranged.

In the carbon nanotube composite structure 10, the micropores of thecarbon nanotube structure 14 are filled with matrix. In one embodimentaccording to FIGS. 4 and 5, the top surface 122 is almost a slicksurface, and the carbon nanotube structure 14 is buried below the topsurface 122. Because the matrix 12 is made of transparent material, thecarbon nanotube structure 14 can be seen from the top surface 122.Referring to FIGS. 6 and 7, in the enlarged SEM image, the carbonnanotube structure 14 can be seen clearly. Some carbon nanotubes 146 inthe carbon nanotube structure 14 protrude from the first surface 142 ofthe carbon nanotube structure 14, the carbon nanotubes 146 protrudingfrom the first surface 142 of the carbon nanotube structure 14 are alsocoated by the matrix 12. During the process and because wettability ofthe liquid matrix and the carbon nanotube structure is good, the liquidmatrix will infiltrate into micropores of the carbon nanotube structure,as such, the carbon nanotube structure will be coated by the liquidmatrix. Even some carbon nanotubes 146 protrude from the carbon nanotubestructure, the protruding carbon nanotubes 146 can be also coated by theliquid matrix. The carbon nanotubes protruding from the first surface142 also protrude from the surface 122. A thickness of the matrix coatedon each of the protruding carbon nanotube is less than 100 nanometers.In some embodiments, the thickness is in a range from about 20nanometers to about 30 nanometers. In FIG. 6, the protruding carbonnanotubes 146 in the carbon nanotube structure 14 are coated by thematrix, and diameters of the protruding carbon nanotubes are about 70 toabout 90 nanometers, and diameters of the carbon nanotubes without beingcoated by the matrix are about 10 to about 30 nanometers. As such,thickness of the matrix material coated on surfaces of the number ofprotruding carbon nanotubes is about 30 nanometers.

Referring to FIGS. 8 and 9, if a water drop is applied on a surface ofthe carbon nanotube structure 14, including a carbon nanotube drawn filmlocated on the surface of the matrix. The water drop will spread on thecarbon nanotube structure 14 along the direction of the carbon nanotubesto form an ellipse structure X having an area about 5.69 mm² because thecarbon nanotubes in the drawn carbon nanotube film are oriented in asame direction. Referring to FIGS. 10 and 11, after the carbon nanotubestructure 14 and the matrix 12 are heated by the microwaves, the carbonnanotube structure 14 is buried under the surface 122. After the waterdrop is dropped on the surface 122, the water drop will spread to form around structure Y having an area about 5.14 mm².

Because the thickness of the matrix above the carbon nanotube structure14 is less than 10 micrometers, the surface 122 of the carbon nanotubecomposite structure is conductive. A square resistance of the surface122 is about 5 KΩ. An experiment proved that the conductivity of thesurface 122 is almost not affected by friction form outside. Theexperiment, according to the following steps, is performed to anembodiment of a carbon nanotube composite structure.

-   providing the carbon nanotube composite structure 10, wherein the    carbon nanotube composite structure 10 is a cuboid, an area of the    surface 122 is about 8×8 mm²;-   applying two electrodes on two opposite side of the surface 122 to    measure the square resistance; and-   scraping the surface 122 with a tip of a needle with a pressure    force about 0.7 Newton (N) between the two electrode, wherein the    needle has a tip covered by cotton .-   During the scraping step, the two electrodes are used to measure the    square resistance, and the square resistance changes little by    scraping the surface 122 for about 50 times. If the carbon nanotube    structure 14 is located on the surface of the matrix without    exposing them to microwaves, the needle will easily destroy the    carbon nanotube structure 14.

Finally, it is to be understood that the above-described embodiments areintended to illustrate rather than limit the present disclosure.Variations may be made to the embodiments without departing from thespirit of the disclosure as claimed. Elements associated with any of theabove embodiments are envisioned to be associated with any otherembodiments. The above-described embodiments illustrate the scope of thedisclosure but do not restrict the scope of the disclosure.

Depending on the embodiment, certain of the steps of methods describedmay be removed, others may be added, and the sequence of steps may bealtered. It is also to be understood that the description and the claimsdrawn to a method may include some indication in reference to certainsteps. However, the indication used is only to be viewed foridentification purposes and not as a suggestion as to an order for thesteps.

1. A method for making a carbon nanotube composite structure, the methodcomprising the following steps: (a) providing a matrix having a surfaceand a carbon nanotube structure; (b) placing the carbon nanotubestructure on the surface of the matrix, wherein the carbon nanotubestructure comprises a plurality of carbon nanotubes; and (c) exposingthe carbon nanotube structure to electromagnetic waves.
 2. The method ofclaim 1, wherein in the step (c), the carbon nanotube structure absorbsthe electromagnetic waves and release heat until the carbon nanotubestructure embeds into the matrix.
 3. The method of claim 2, wherein inthe step (c), the carbon nanotube structure defines a plurality ofmicropores, and material of the matrix seeps into the plurality ofmicropores.
 4. The method of claim 1, wherein in the step (b), thecarbon nanotube structure comprises at least one carbon nanotube film,and the at least one carbon nanotube film is a drawn carbon nanotubefilm comprising a plurality of successively oriented carbon nanotubesegments joined end-to-end by van der Waals force therebetween, eachcarbon nanotube segment comprises carbon nanotubes parallel to eachother, and combined by van der Waals force therebetween, and the carbonnanotubes of the drawn carbon nanotube film are substantially alignedalong a same direction.
 5. The method of claim 4, wherein the carbonnanotube structure comprises a plurality of stacked drawn carbonnanotube films, and the plurality of stacked drawn carbon nanotube filmsare fabricated by following steps: N1: providing an array of carbonnanotubes and a frame; N2: pulling out a drawn carbon nanotube film fromthe array of carbon nanotubes; N3: adhering the carbon nanotube film tothe frame; N4: repeating steps N2 and N3, depositing each successivecarbon nanotube film on a preceding drawn carbon nanotube film, therebyachieving at least a two-layer drawn carbon nanotube film; and N5:peeling the plurality of stacked drawn carbon nanotube films off theframe to achieve the plurality of stacked drawn carbon nanotube films.6. The method of claim 5, wherein the step (b) further comprises asubstep of applying an organic solvent to the plurality of stacked drawncarbon nanotube films.
 7. The method of claim 1, wherein in the step(b), the carbon nanotube structure is a pure structure of carbonnanotubes.
 8. The method of claim 1, wherein in the step (c), a power ofthe electromagnetic waves is in a range from about 200 W to about 2000W.
 9. The method of claim 1, wherein in the step (c), theelectromagnetic waves comprises radio frequency, microwave, nearinfrared or far infrared.
 10. The method of claim 9, wherein theelectromagnetic waves are microwaves.
 11. The method of claim 10,wherein a power of the microwaves is in a range from about 200 W toabout 1500 W.
 12. The method of claim 1, wherein in step (c), the carbonnanotube structure located on the surface of the matrix is placed in achamber filled with the electromagnetic waves.
 13. The method of claim12, wherein in step (c), the carbon nanotube structure and the matrixare kept in the chamber for about 1 second to about 300 seconds.
 14. Themethod of claim 1, wherein step (c) is carried out in vacuum environmentof about 10⁻² Pascals to about 10⁻⁶ Pascals or in a specific atmosphereof protective gases including nitrogen gas and inert gases.
 15. Themethod of claim 1, wherein the matrix is made of insulative materialshaving a melting point less than 600° C.
 16. A method for making acarbon nanotube composite structure, the method comprising the followingsteps: (a) providing a matrix having a surface and a carbon nanotubestructure; (b) placing the carbon nanotube structure on the surface ofthe matrix, the carbon nanotube structure comprising a plurality ofcarbon nanotubes and a plurality of micropores; and (c) exposing thecarbon nanotube structure to microwaves for about 1 second to about 300seconds.
 17. The method of claim 16, wherein in step (c), the carbonnanotube structure is formed on the matrix by a coating method or aspraying method.
 18. The method of claim 16, wherein step (c) is carriedout in vacuum environment of about 10⁻² Pascals to about 10⁻⁶ Pascals orin a specific atmosphere of protective gases comprising and one or moreinert gases.
 19. The method of claim 18, wherein in step (c), the carbonnanotube structure absorbs the microwaves and is heated to hightemperature, the matrix of the surface is heated by the carbon nanotubestructure and is melted to permeate through the plurality of microporesof the carbon nanotube structure.
 20. The method of claim 19, whereinthe matrix of the surface covers the carbon nanotube structure, adistance between each of the plurality of carbon nanotubes and thesurface is less than 10 micrometers.